spelling error

--- a/src/HOL/IMP/Big_Step.thy	Mon Jan 26 14:34:10 2015 +0100
+++ b/src/HOL/IMP/Big_Step.thy	Mon Jan 26 14:40:13 2015 +0100
@@ -6,7 +6,7 @@
 
 text {*
 The big-step semantics is a straight-forward inductive definition
-with concrete syntax. Note that the first paramenter is a tuple,
+with concrete syntax. Note that the first parameter is a tuple,
 so the syntax becomes @{text "(c,s) \<Rightarrow> s'"}.
 *}